Adipocyte fatty acid-binding protein and mitochondrial enzyme activities in muscles as relevant indicators of marbling in cattle

¹ INRA, UR1213 Herbivores, Site de Theix, F-63122 Saint-Genès-Champanelle, France
² UPRA France Limousin Sélection, Lanaud, F-87220 Boisseuil, France
³ Murdoch University, Division of Veterinary and Biomedical Sciences, Perth, Australia

^* To whom correspondence should be addressed. E-mail: jurie{at}clermont.inra.fr.

	Abstract

Marbling is an important criterion for beef quality grading in many countries. The purpose of the present study was to utilise the natural genetic variation to identify major metabolic indicators of marbling in cattle different in terms of genotypes. Rectus abdominis (RA, oxidative), semitendinosus (ST, glycolytic) and longissimus thoracis (LT, oxido-glycolytic) muscles were taken from steers of different genotypes which expressed either high (Angus n = 16; Crossbred Angus x Japanese Black n = 10) or low (Limousin n = 12) levels of marbled meat. Muscles from Angus and Crossbred steers were characterized, as expected, by a greater triacylglycerol (TAG) content (P < 0.001) and also by greater protein contents of fatty acid-binding protein specific for heart and muscles (H-FABP) (P < 0.001 for RA and P < 0.05 for LT muscle) or for adipocyte (A-FABP) (P < 0.001 for RA and LT muscles). Moreover, oxidative enzyme activities (-hydroxyacyl-CoA dehydrogenase [HAD], citrate synthase [CS], isocitrate dehydrogenase [ICDH], cytochrome-c oxidase [COX]) were greater (P < 0.01 to 0.001) in the three studied muscles, whereas glycolytic enzyme activities (phosphofructokinase [PFK], lactate dehydrogenase [LDH]) were lower (P < 0.001) in RA muscle in Angus and Crossbred steers compared to Limousin steers. Significant correlations were observed between TAG content and H- and A-FABP protein contents, oxidative (r + 0.55, P < 0.001) or glycolytic enzyme activities (r - 0.47, P < 0.001), when the three studied genotypes and muscles were considered as a whole. In addition, A-FABP protein content and some oxidative enzyme activities were significantly correlated with TAG content independently of the genotype and muscle effects. In conclusion, A-FABP protein content, as well as oxidative enzyme activities may be used as indicators of the ability of steers from extreme genotypes to deposit intramuscular fat.

Key Words: Triacylglycerol, Marbling, Fatty acid-binding protein, Muscle metabolism, Genotype, Steers

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